Adjustable time limit device



Aug. 27, 1946. 'B, ,MMEL 2,40 ,377

ADJUSTABLE TIME LIMIT DEVI CE Filed July 20, 1943 2 Sheets-Sheet l WITNESSES: INVENTOR 5% 7% r 5040/) film/776A BY ATTORNEY 1946- R. B. IMMIEL 7 2,406,377

ADJUSTABLE TIME LIMIT DEVICE Filed July 20, 1945 2 Sheets-Sheet 2 WITNESSES: I INVENTOR if EOJOfiJT/mmefi BY I v M M M :3 Wmm ATTORNEY .teristic Patented Aug. 27, I946 Ralph E. Immel, Wilkinsburg,

Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh Pa., a corporation of Pennsylvania Application July 20, 1943, Serial No. 495,467 3 Claims. (Cl. 175-372) My invention relates to direct-current energized contactors, switches, relays and the like after .1

n tically reluctant shims or netic circuit of the device and to adjust turn spring of the relay armature'relative to the magnetic forces so as delays.

However, the time-limit devices of this type, as 7st etofore available, offer a rather limited or no appreciable range of adjustability; that is, the devices are usually manufactured for a given time limit and, once in the finished state, do not'permit changing the limit to an appreciable extent, or require for this purpose an extensive disassembly or reconstruction of the magnetic structure.

In one of the known time-limit relays, a plurality of copper discs are placed on the magnet core of the relay, and the time limit is adjusted byselecting the number of discs thus employed.

The adjustment has to be made during the course of manufacture and cannot be changed Without severing the permanently interconnected parts of the magnetic structure from one another and from their common base or support once the relay in been assembled in the factory; and it is also diilicult to obtain accurate and definitely predetermined time constants since the delay characof this relay depends not only on the number or total cross section of the copper discs, but also on their location relative to the magnet core and armature.

It is an object of my invention to provide an elec romagnetic time-limit device Which aiTords adjustment and change of the time limit with considerably greater ease than afforded by the known devices of this type. I

More specifically, in this aspect, the invention aims at providing a type of electromagnetic contactor Whose manufacture and assembly can be substantially completed regardless of the particbody from its supporting frame or permanent cir cuit connections.

Another object in line with the foregoing is to permit a ready adjustment or change of the time limit by the user of the device, 1. e. outside the factory or after the device has been installed in its ultimateplace of operation.

While the invention involves using a selective plurality of short-circuited Winding elements, it is also among its objects to render the time-limit adjustment more accurate and definitely predetermined than heretofore obtainable. ular, a definite dependence of the time limit on the selected windings regardless of their specific location along the them, is intended.

Having these objects in mind, I propose according to this invention, to arrange the magnetizing coils of time-limit devices so that they surround the appertaining magnet core with sumcient play to form" a peripheral interstice, and to provide of the inserted Winding elements relative tothe core and determined only by the total cross section of the windings, or, if the elements are substantially alike, only on their selected number.

According to another feature of my invention, the magnet core and armature of a time-limit device as relferredto above are attached to a magnetic supporting structure so that the armature is readily removable, While a selective plurality of annular ture when the latter is removed.

In still another aspect, the invention provides an electromagnetic time-limit device with a fixed 3 interfere with the insertion or removal of annular elements.

The invention is represented by the embodiments shown in the drawings, in which:

Figure 1 is a top view of a timing relay.

Fig. 2 is a part-sectional side elevation.

Fig. 3 is a front elevation of the same relay, while Fig. ashows a diagram of time delays in dependence upon the selected number of short circuited winding elements, and;

Figs. 5 through 7 are side elevations of three other embodiments distinguished by different designs and arrangements of a magnetically re luctant shim element.

Referring to Figs. 1, 2 and 3, numeral I denotes a magnetizable supporting structure consisting, for instance, of an angular piece of iron. An elongated cylindrical magnet core 2 is mounted on the support I and carries at one end a shim 3 and a pole piece 4, both attached to the core 2 by means of a screw 5. The shim consists of a material of high magnetic reluctance, for instance of a disc made of brass. Th screw 5 may also consist of brass or the like reluctant material. It should be noted that the diameter of the shim 3 and of the pole piece 4 are equal to the diameter of the core member 2 so that the entire core assembly has a straight cylindrical shape over the entire longitudinal extent of the assembly.

A magnetic armature 6 has its upper edge placed against the support I and is held in position by means of an abutment plate 1 which is firmly attached to the structure I. The upper edge of the armature 6 contacting the structure I is cut in an acute angle in order to permit the armature 3 rotational movements about the fulcrum formed by the armature edge. A bracket member 9 is firmly secured to the armature 6, the lower end of this bracket, in the illustrated position, rests against a stationary abutment formed by a metal piece 8 which is mounted on the supporting structure I. This abutment piece limits the motion of the armature 6 in the direction away from the magnet core 2 and as illustrated, may contain a screw for adjusting the inactive position of the armature.

A bolt 26 has its lower end journalled to the bracket member 9 and carrie a helical spring l whose lower end rests against a nut 21 engaging the bolt 26, while the upper end of the spring l0 abuts against the bracket member 9. The bolt 26 carries a cross bar H which bridges a recess formed by the abutment plate 1. The two ends of the cross bar are bent away at right angles and form lugs l2 which engage corresponding openings l3 of the abutment plate I.

When the relay is in assembled condition as represented by Figs. 1, 2 and 3, the spring I0 is under compression and hence pulls the cross bar ll against the abutment plate 1 thereby securing the lugs l2 in their engagement with the opening l3 while holding the armature 6 and the bracket 9 in the position shown in Fig. 2, in which the bracket member 9 rests against the abutment member 8. In this condition, the compressed spring [0 biases the armature 6 away from the core 2.

A contact member [4 carrying two contact pieces of silver is attached to the armature assembly and cooperates with two stationary contacts l and I6 which are firmly connected with the supporting structure I and are in electric contact with terminals l1 and I8, respectively. In

the

the illustrated position, the contact member H is moved away from the stationary contacts [5 and Hi. When the armature is attracted by the magnet core 2 against the force of spring in, the contact member l4 moves against the stationary contacts and establishes an electric connection between terminals l1 and I8 through contact members l5, I l and US.

As apparent from Figs. 1, 2 and 3, the armature 6 and all other parts assembled therewith can be readily removed from the supporting structure I and its appertaining parts by pulling the cross bar ll out of engagement with the openings (3 of the abutment plate I and then moving the cross bar and the armature B away from the magnet core 2. In the opposite manner, the assembly can be reinserted into the relay. When the armature assembly is removed, the front surface of the core structure is readily accessible.

A magnetizing direct current coil is is mounted on a supporting structure I so as to surround the core member 2 with sufficient play to form a cylindric interstice between the core and coil. Two bolts 20 and 2! serve for fastening the supporting structure I to a suitable base.

Referring more particularly to Fig. 2, it will be seen that the just-mentioned interstice between the magnet core and the magnetizing coil contains a plurality of annular elements 22. In the illustrated embodiments, these elements consist of slugs or rings of a material of relatively good electric conductivity so that each of them forms a short circuited current path around the magnet core assembly of elements 2, 3 and 4. The elements 22 ma consist of copper rings although other metals, such as iron, are also applicable. The elements 22 are so dimensioned that they have substantially the same size and can easily be slipped on or off the magnet core when the armature assembly is removed from the stationary relay structure.

The electric resistance of the short circuited current path, assuming that the same material is employed for all elements 22, depends on the total cross section of the elements placed between the magnet core and the magnetizig coil. This total resistance and cross section can be adjusted by changing the number of elements 22. That is, in order to increase the time constant of the device the maximum number of elements 22, i. e. six elements in the illustrated embodiment, are to be inserted into the cylindrical interstice. For obtaining a lower time constant, the number of element 22 is reduced, the minimum retardation of relay action being obtained when all elements 22 are removed from the interstice. The elements may have holes such as shown at 28 in Fig. 2 or may be otherwise designed to facilitate their removal.

Due to the above-described possibility of removing the armature assembly and by virtue of the fact that the space for receiving the short circuited winding elements 22 is open towards the armature and not obstructed by any part like the shim 3 and the pole piece 4, the relay can easily be adjusted to seven different time delays. Since the time constant, though to a lesser degree, is also dependent on the adjustment force of the spring ID, the relay permits also an adjustment of its time constant to values intermediate those obtained by the above-mentioned selection in the number of the winding elements 22. In other words, the adjusting nut 21 of spring l0 affords a vernier adjustment of intermediate time delay values.

Due to the fact that all short circuiting winding elements 22 lie within the range of the magnet core surrounded by the magnetizing coil IS, the location of the individual element 22 along the core 2 has no noticeable efiect on the time limit. Thus, even if only one element 22 is inserted into the relay, the time limit remains the same whether the element lies next to the supporting structure I, or close to the armature, or in some intermediate position.

The time delay curves shown in Fig. 4 are based on test results obtained with a indicates the number of elements 22 inserted into the coil while the ordinate values denote the time delays in seconds. The results were obtained by energizing the magnetizing core of the relay and then interrupting the energizing current. time elapsing cates the delays obtained with a relatively low contact pressure, i. e. a corresponding adjustment of the relay spring 10, while curve D refers to the same relay with the spring l adjusted for a higher contact pressure. In both cases, the period of delay was definitely determined by the number of winding elements 22. The two curves indicate that any period of delay between the netizable supporting structure I. In this case,

the shim 29 remams permanently attached to the relay is adjusted by "constructions are so designed that they do not possibility and ease of controlling the time constant by inserting a selected number of the short circuiting winding elements.

While I have shown and described a limited number of modifications within the scope of my invention, it will be apparent from the foregoing to those skilled in the art that other embodiments may be devised without departing from the principles and teaching of this disclosure. Therefore, I wish this specification to be considered as illu trative and not in a limiting sense.

I claim as my invention:

1. An electromagnetic time-limit device, c0mprising a magnetic field structure having a core, an armature pivotally linked to said structure and being biased away from one end of said core to be attracted thereby when core is magnetized, a magnetizing coil surrounding said core with willcient spacing to form an interstice around and along said core for the reception of short-circuit- 2. An electromagnetic time-limit device, comprising a magnetic frame structure, an elongated core having one end attached to said structure to be insertable and removable from the side of said free end when said assembly is removed from said structure, whereby the time-limit of the device is adjustable by a corresponding selection of the inserted element.

3. An electromagnetic time-limit prising a magnetic frame structure, an elongated elements, a plurality of short-circuiting cylindrical ring elements the time limit of the device by a corresponding selection of said elements, said elements having a radial width nearly equal to that of said interstice.

RALPH B. IMIMEL. 

